Apparatus and method for light-irradiation heat treatment

ABSTRACT

Light is applied for preheating from a halogen lamp to a lower surface of a semiconductor wafer supported on a susceptor within a chamber. Thereafter, flash light is applied for flash heating from a flash lamp to an upper surface of the semiconductor wafer. Treatment gas supplied from a gas supply source is heated by a heater, and supplied into the chamber. A flow amount control valve is provided to increase a flow amount of the treatment gas supplied into the chamber. Contaminants discharged from a film of the semiconductor wafer during heat treatment are discharged to the outside of the chamber with a gas flow formed by a large amount of high-temperature treatment gas supplied into the chamber to reduce contamination inside the chamber.

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a heat treatment apparatus and a heattreatment method for heating a sheet precision electronic substrate(hereinafter, simply referred to as a “substrate”), such as asemiconductor wafer, by irradiating the substrate with light.

2. Description of the Background Art

In the process of manufacturing a semiconductor device, the introductionof impurities is an essential step for forming pn junctions in asemiconductor wafer. At present, it is common to introduce impurities byion implantation and subsequent annealing. Ion implantation is atechnique for physically doping impurities by causing impurity elementssuch as boron (B), arsenic (As), or phosphorus (P) to be ionized andcollide with a semiconductor wafer with a high acceleration voltage. Thedoped impurities are activated by annealing. At this time, if theannealing time becomes about several seconds or longer, the dopedimpurities are deeply diffused by heat, and as a result, the junctiondepth may become too deeper than required and hinder the formation of agood device.

In view of this, flash-lamp annealing (FLA) is recently attractingattention as an annealing technique that allows semiconductor wafers tobe heated in an extremely short time. Flash-lamp annealing is a heattreatment technique using xenon flash lamps (hereinafter, “flash lamps”simply referred to indicate xenon flash lamps) to irradiate the surfaceof a semiconductor wafer with flash light so that the temperature ofonly the surface of the semiconductor wafer that is doped withimpurities is raised in an extremely short time (several milliseconds orless).

The radiation spectral distribution of xenon flash lamps ranges fromultraviolet to near-infrared regions, with the xenon flash lamps havingshorter wavelengths than conventional halogen lamps, and approximatelycoincides with the fundamental absorption band of silicon semiconductorwafers. Thus, in the case where flash light is applied from xenon flashlamps to a semiconductor wafer, less light will be transmitted throughthe semiconductor wafer and therefore it is possible to quickly raisethe temperature of the semiconductor wafer. It has also been found thatthe temperature of only the vicinity of the surface of the semiconductorwafer will selectively be raised with extremely short-time applicationof flash light for several milliseconds or less. Thus, extremelyshort-time temperature rise with the xenon flash lamps enables theimpurities to be activated simply without being diffused deeply.

As examples of such a heat treatment apparatus using xenon flash lamps,U.S. Pat. No. 4,649,261 and U.S. 2003/0183612 A1 disclose heat treatmentapparatuses that achieve desirable heat treatment with a combination ofpulsed light-emitting lamps such as flash lamps that are arranged on thefront side of a semiconductor wafer and continuous lighting lamps suchas halogen lamps that are arranged on the rear side of the semiconductorwafer. In the heat treatment apparatuses disclosed in U.S. Pat. No.4,649,261 and U.S. 2003/0183612, a semiconductor wafer is preheated to acertain degree of temperature with, for example, halogen lamps, and thenthe temperature of the semiconductor wafer is raised to a desiredtreatment temperature by pulse heating with flash lamps.

Some semiconductor wafers treated with flash-lamp annealing containvarious types of films such as a resist film. When flash light isapplied for heat treatment to this type of semiconductor wafercontaining films, an inner wall of a chamber accommodating thesemiconductor wafer, and a structure inside the chamber such as asusceptor may be contaminated. It is estimated that this contaminationis caused by adhesion of carbon contaminants to the structure inside thechamber at the time of combustion of the respective films on thesemiconductor wafer by flash heating. Contamination of the structureinside the chamber becomes a contamination source for a subsequentsemiconductor wafer. During light irradiation, light reflected on aninner wall surface of the chamber is also applied to the semiconductorwafer. When the inner wall surface of the chamber is contaminated,reflectance at the contaminated portion lowers. In this case, in-planetemperature distribution of the semiconductor wafer becomes non-uniformduring irradiation of light. This condition influences a treatmentresult of flash heating treatment, and produces a bend of thesemiconductor wafer in correspondence with the non-uniform temperaturedistribution. Moreover, in the case of the structure which disposeslamps on both surfaces of the semiconductor wafer as disclosed in U.S.Pat. No. 4,649,261 and U.S. 2003/0183612, light transmittance lowerswhen the susceptor is contaminated.

SUMMARY OF THE INVENTION

The present invention is directed to a heat treatment apparatus whichheats a substrate by irradiating the substrate with light.

According to one aspect of the present invention, a heat treatmentapparatus includes: a chamber that accommodates a substrate; a susceptorprovided in the chamber and supporting the substrate; a lightirradiation part that applies light to the substrate supported on thesusceptor; a gas supply part that supplies treatment gas into thechamber; and a gas heater that heats the treatment gas supplied from thegas supply part to the chamber.

According to this structure, contaminants discharged from the substrateduring heat treatment are discharged to the outside of the chamber witha flow of high-temperature treatment gas formed within the chamber toreduce contamination inside the chamber.

It is preferable that there is further provided a flow amount increasingpart that increases a flow amount of the treatment gas supplied from thegas supply part to the chamber.

According to this structure, contaminants are effectively discharged tothe outside of the chamber.

The present invention is also directed to a heat treatment method whichheats a substrate by irradiating the substrate with light.

According to another aspect of the present invention, a heat treatmentmethod includes steps of: (a) supporting a substrate on a susceptorwithin a chamber; (b) supplying treatment gas into the chamber; and (c)applying light to the substrate supported on the susceptor. The step (b)includes a step of (b-1) heating the treatment gas supplied to thechamber.

According to this structure, contaminants discharged from the substrateduring heat treatment are discharged to the outside of the chamber witha flow of high-temperature treatment gas formed within the chamber toreduce contamination inside the chamber.

It is preferable that the step (b) further includes a step of (b-2)increasing a flow amount of the treatment gas supplied to the chamber.

According to this structure, contaminants are effectively discharged tothe outside of the chamber.

Accordingly, an object of the present invention is to reducecontamination within the chamber.

These and other objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view illustrating aconfiguration of a heat treatment apparatus according to the presentinvention;

FIG. 2 is a perspective view of an overall external view of a holder;

FIG. 3 is a plan view of the holder as viewed from above;

FIG. 4 is a side view of the holder as viewed from one side;

FIG. 5 is a plan view of a transfer mechanism;

FIG. 6 is a side view of the transfer mechanism; and

FIG. 7 is a plan view illustrating arrangement of a plurality of halogenlamps.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of the present invention will bedescribed in detail with reference to the drawings.

FIG. 1 is a longitudinal cross-sectional view illustrating aconfiguration of a heat treatment apparatus 1 according to the presentinvention. The heat treatment apparatus 1 of this preferred embodimentis a flash-lamp annealing apparatus for heating a disk-shapedsemiconductor wafer W as a substrate by irradiating the semiconductorwafer W with flash light. The size of the semiconductor wafer W to betreated is not particularly limited. For example, the semiconductorwafer W has a diameter of 300 mm or 450 mm. The semiconductor wafer W isdoped with impurities before being transported into the heat treatmentapparatus 1, and the doped impurities are activated through heattreatment by the heat treatment apparatus 1. To facilitateunderstanding, the dimensions and number of each part are exaggerated orsimplified as necessary in FIG. 1 and subsequent drawings.

The heat treatment apparatus 1 includes a chamber 6 that houses thesemiconductor wafer W, a flash heater 5 with a plurality of built-inflash lamps FL, and a halogen heater 4 with a plurality of built-inhalogen lamps HL. The flash heater 5 is provided above the chamber 6,and the halogen heater 4 is provided below the chamber 6.

The heat treatment apparatus 1 further includes, within the chamber 6, aholder 7 that holds the semiconductor wafer W in a horizontal positionand a transfer mechanism 10 for transferring the semiconductor wafer Wbetween the holder 7 and the outside of the heat treatment apparatus 1.The heat treatment apparatus 1 includes a mechanism which suppliesheated treatment gas into the chamber 6. The heat treatment apparatus 1further includes a controller 3 that controls operating mechanismslocated in the halogen heater 4, the flash heater 5, and the chamber 6for heat treatment of the semiconductor wafer W.

The chamber 6 is configured by mounting quartz chamber windows on thetop and bottom of a tubular chamber side portion 61. The chamber sideportion 61 has a generally tubular shape that is open at the top and thebottom, the opening at the top being equipped with and closed by anupper chamber window 63 and the opening at the bottom being equippedwith and closed by a lower chamber window 64. The upper chamber window63, which forms the ceiling of the chamber 6, is a disc-shaped membermade of quartz and functions as a quartz window that allows flash lightemitted from the flash heater 5 to pass through into the chamber 6. Thelower chamber window 64, which forms the floor of the chamber 6, is alsoa disc-shaped member made of quartz and functions as a quartz windowthat allows light emitted from the halogen heater 4 to pass through intothe chamber 6.

A reflection ring 68 is mounted on the upper part of the inner wallsurface of the chamber side portion 61, and a reflection ring 69 ismounted on the lower part thereof. Both of the reflection rings 68 and69 have an annular shape. The upper reflection ring 68 is mounted bybeing fitted from above the chamber side portion 61. The lowerreflection ring 69 is mounted by being fitted from below the chamberside portion 61 and fastened with screws (not shown). In other words,the reflection rings 68 and 69 are both removably mounted on the chamberside portion 61. The chamber 6 has an inner space that is surrounded bythe upper chamber window 63, the lower chamber window 64, the chamberside portion 61, and the reflection rings 68 and 69 and that is definedas a heat treatment space 65.

With the reflection rings 68 and 69 mounted on the chamber side portion61, the chamber 6 has a recessed portion 62 in its inner wall surface.That is, the recessed portion 62 is formed by being surrounded by acentral portion of the inner wall surface of the chamber side portion 61on which the reflection rings 68 and 69 are not mounted, a lower endface of the reflection ring 68, and an upper end face of the reflectionring 69. The recessed portion 62 is horizontally formed in an annularshape in the inner wall surface of the chamber 6 and surrounds theholder 7 that holds the semiconductor wafer W.

The chamber side portion 61 and the reflection rings 68 and 69 are eachmade of a metal material (e.g., stainless steel) having excellentstrength and heat resistance. The inner circumferential surfaces of thereflection rings 68 and 69 are mirror-finished by electrolytic nickelplating. The chamber side portion 61 has a transport opening (throat) 66through which the semiconductor wafer W is transported into and out ofthe chamber 6. The transport opening 66 is openable and closable with agate valve 185. The transport opening 66 is communicatively connected tothe outer circumferential surface of the recessed portion 62. Whenopened by the gate valve 185, the transport opening 66 allows thesemiconductor wafer W to be transported into and out of the heattreatment space 65 from the transport opening 66 through the recessedportion 62. When the transport opening 66 is closed by the gate valve185, the heat treatment space 65 in the chamber 6 becomes an enclosedspace.

The chamber 6 also includes a gas supply port 81 in the upper part ofthe inner wall. The gas supply port 81 is a port through which treatmentgas is supplied to the heat treatment space 65. The gas supply port 81is formed at a position above the recessed portion 62 and may be formedin the reflection ring 68. The gas supply port 81 is communicativelyconnected to a gas supply pipe 83 via a buffer space 82 that is formedin an annular shape inside the side wall of the chamber 6. The gassupply pipe 83 is connected to a gas supply source 85. A valve 84, aflow amount control valve 21, and a heater 22 are interposed in the pathof the gas supply pipe 83. The type of the treatment gas supplied fromthe gas supply source 85 is not particularly limited, but may bearbitrarily selected in accordance with treatment purposes. For example,the treatment gas may be nitrogen (N₂), argon (Ar), helium (He) or otherinert gases, or oxygen (O₂), hydrogen (H₂), chloride (Cl₂), hydrogenchloride (HCl), ozone (O₃), ammonia (NH₃), fluorine-containing gases, orother reactive gases.

When the valve 84 is opened, treatment gas is supplied from the gassupply source 85 into the buffer space 82. The treatment gas flowinginto the buffer space 82 spread out in the buffer space 82 which haslower fluid resistance than that of the gas supply port 81. Thereafter,the treatment gas is supplied through the gas supply port 81 into theheat treatment space 65. The flow amount of the treatment gas flowingthrough the gas supply pipe 83 and reaching the heat treatment space 65is regulated by the flow amount control valve 21. Accordingly, the gassupply source 85 and the valve 84 correspond to a gas supply part forsupplying treatment gas into the chamber 6, while the flow amountcontrol valve 21 corresponds to a flow amount increasing part forincreasing the flow amount of the treatment gas supplied to the chamber6. The flow amount increasing part may be constituted by a massflowcontroller instead of the flow amount control valve 21.

The heater 22 heats treatment gas flowing in the gas supply pipe 83. Thetreatment gas heated by the heater 22 is supplied from the gas supplyport 81 to the heat treatment space 65. Accordingly, the heater 22corresponds to a gas heater for heating treatment gas supplied to thechamber 6.

The chamber 6 also has a gas exhaust port 86 through which the gas inthe heat treatment space 65 is exhausted, in the lower part of the innerwall. The gas exhaust port 86 is formed at a position below the recessedportion 62 and may be formed in the reflection ring 69. The gas exhaustport 86 is communicatively connected to a gas exhaust pipe 88 via abuffer space 87 that is formed in an annular shape inside the side wallof the chamber 6. The gas exhaust pipe 88 is connected to an exhaustpart 190. The gas exhaust pipe 88 has a valve 89 interposed on the wayof its path. When the valve 89 opens, the gas in the heat treatmentspace 65 is discharged from the gas exhaust port 86 through the bufferspace 87 into the gas exhaust pipe 88. A configuration is also possiblein which a plurality of gas supply ports 81 and a plurality of gasexhaust ports 86 are provided along the circumference of the chamber 6or in which the gas supply port 81 and the gas exhaust port 86 have slitshapes. The gas supply source 85 and the exhaust part 190 may bemechanisms provided in the heat treatment apparatus 1, or may beutilities in a factory where the heat treatment apparatus 1 isinstalled.

One end of the transport opening 66 is also connected to a gas exhaustpipe 191 through which the gas in the heat treatment space 65 isdischarged. The gas exhaust pipe 191 is connected to the exhaust part190 via a valve 192. When the valve 192 opens, the gas in the chamber 6is discharged through the transport opening 66.

FIG. 2 is a perspective view illustrating an overall external view ofthe holder 7. FIG. 3 is a plan view of the holder 7 as viewed fromabove, and FIG. 4 is a side view of the holder 7 as viewed from oneside. The holder 7 includes a base ring 71, connecting parts 72, and asusceptor 74. The base ring 71, the connecting parts 72, and thesusceptor 74 are all made of quartz. That is, the entire holder 7 ismade of quartz.

The base ring 71 is a quartz member having an annular shape. The basering 71 is placed on the bottom face of the recessed portion 62 andthereby supported on the wall surface of the chamber 6 (see FIG. 1). Onthe upper surface of the annular base ring 71, a plurality of (in thepresent embodiment, four) connecting parts 72 are provided upright alongthe circumference of the base ring 71. The connecting parts 72 are alsoquartz members and fixedly attached to the base ring 71 by welding. Notethat the base ring 71 may have an arc shape that is an annular shapewith a missing part.

The flat plate-like susceptor 74 is supported by the four connectingparts 72 provided on the base ring 71. The susceptor 74 is a generallycircular flat plate-like member made of quartz. The diameter of thesusceptor 74 is greater than the diameter of the semiconductor wafer W.That is, the susceptor 74 has a plane size greater than the plane sizeof the semiconductor wafer W. On the upper surface of the susceptor 74,a plurality of (in the present embodiment, five) guide pins 76 areprovided upright. The five guide pins 76 are provided along thecircumference of a circle that is concentric with the outercircumferential circle of the susceptor 74. The diameter of the circlealong which the five guide pins 76 are located is slightly greater thanthe diameter of the semiconductor wafer W. Each guide pin 76 is alsomade of quartz. Note that the guide pins 76 may be made integrally withthe susceptor 74 from a quartz ingot, or may be processed separately andattached to the susceptor 74 by methods such as welding.

The four connecting parts 72 provided upright on the base ring 71 andthe underside of the peripheral portion of the susceptor 74 are fixedlyattached to each other by welding. That is, the susceptor 74 and thebase ring 71 are fixedly coupled to each other by the connecting parts72, which makes the holder 7 an integral molding member of quartz. Thisbase ring 71 of the holder 7 is supported on the wall surface of thechamber 6, and thereby the holder 7 is attached to the chamber 6. Withthe holder 7 attached to the chamber 6, the generally circularplate-like susceptor 74 is in a horizontal position (a position at whichthe normal coincides with the vertical direction). The semiconductorwafer W transported into the chamber 6 is placed and held in ahorizontal position on the susceptor 74 of the holder 7 attached to thechamber 6. By disposing the semiconductor wafer W inward of the circleformed by the five guide pins 76, a positional shift of thesemiconductor wafer W in the horizontal direction is prevented. Notethat the number of guide pins 76 is not limited to five, and may be anarbitrary number as long as the positional shift of the semiconductorwafer W is prevented.

As illustrated in FIGS. 2 and 3, the susceptor 74 has a verticallypenetrating opening 78 and a cut-out portion 77. The cut-out portion 77is provided to pass through the tip of a probe of a contact-typethermometer 130 using a thermocouple. On the other hand, the opening 78is formed to allow a radiation thermometer 120 to receive radiation(infrared light) applied from the lower surface of the semiconductorwafer W held by the susceptor 74. The susceptor 74 further has fourthrough holes 79 that lift pins 12 of the transfer mechanism 10, whichwill be described later, pass through to transfer the semiconductorwafer W.

FIG. 5 is a plan view of the transfer mechanism 10. FIG. 6 is a sideview of the transfer mechanism 10. The transfer mechanism 10 includestwo transfer arms 11. The transfer arms 11 have an arc shape thatextends substantially along the annular recessed portion 62. Eachtransfer arm 11 has two upright lift pins 12. Each transfer arm 11 ispivotable by a horizontal movement mechanism 13. The horizontal movementmechanism 13 horizontally moves the pair of transfer arms 11 between atransfer operation position (position indicated by the solid line inFIG. 5) at which the semiconductor wafer W is transferred to the holder7 and a retracted position (position indicated by the dasheddouble-dotted line in FIG. 5) at which the transfer arms 11 do notoverlap the semiconductor wafer W held by the holder 7 in a plan view.The horizontal movement mechanism 13 may be a mechanism for separatelypivoting the transfer arms 11 by separate motors, or may be a mechanismfor using a link mechanism to pivot the pair of transfer arms 11 inconjunction with each other by a single motor.

The pair of transfer arms 11 are also elevated and lowered together withthe horizontal movement mechanism 13 by an elevating mechanism 14. Whenthe elevating mechanism 14 elevates the pair of transfer arms 11 at thetransfer operation position, a total of four lift pins 12 pass throughthe through holes 79 (see FIGS. 2 and 3) formed in the susceptor 74, andthe upper ends of the lift pins 12 protrude from the upper surface ofthe susceptor 74. On the other hand, when the elevating mechanism 14lowers the pair of transfer arms 11 at the transfer operation positionto pull the lift pins 12 out of the through holes 79, and the horizontalmovement mechanism 13 moves the pair of transfer arms 11 to open thetransfer arms 11, each transfer arm 11 moves to its retracted position.The retracted positions of the pair of transfer arms 11 are directlyabove the base ring 71 of the holder 7. Because the base ring 71 isplaced on the bottom face of the recessed portion 62, the retractedpositions of the transfer arms 11 are inside the recessed portion 62.Note that, in the vicinity of the area where the driving parts (thehorizontal movement mechanism 13 and the elevating mechanism 14) of thetransfer mechanism 10 are provided, an exhaust mechanism (not shown) isalso provided so that the atmosphere around the driving parts of thetransfer mechanism 10 is discharged to the outside of the chamber 6.

Referring back to FIG. 1, the flash heater 5 provided above the chamber6 is configured to include, inside a casing 51, a light source having aplurality of (in the present embodiment, 30) xenon flash lamps FL and areflector 52 that is provided to cover the top of the light source. Thecasing 51 of the flash heater 5 has a lamp-light radiation window 53attached to the bottom. The lamp-light radiation window 53, which formsthe floor of the flash heater 5, is a plate-like quartz window made ofquartz. Since the flash heater 5 is disposed above the chamber 6, thelamp-light radiation window 53 opposes the upper chamber window 63. Theflash lamps FL apply flash light to the heat treatment space 65 fromabove the chamber 6 via the lamp-light radiation window 53 and the upperchamber window 63 to perform flash heating for the semiconductor waferW.

The flash lamps FL are each a rod-shaped lamp having an elongatedcylindrical shape and are arrayed in a plane such that theirlongitudinal directions are parallel to one another along the majorsurface of the semiconductor wafer W held by the holder 7 (i.e., alongthe horizontal direction). Thus, a plane formed by the array of theflash lamps FL is also a horizontal plane.

The xenon flash lamps FL each include a rod-shaped glass tube (dischargetube) and a trigger electrode provided on the outer circumferentialsurface of the glass tube, the glass tube containing a xenon gas sealedtherein and including an anode and a cathode that are disposed atopposite ends of the glass tube and connected to a capacitor. Since thexenon gas is electrically an insulator, no electricity passes throughthe glass tube in a normal state even if electric charge is stored inthe capacitor. However, if an electrical breakdown occurs due to theapplication of a high voltage to the trigger electrode, the electricitystored in the capacitor instantaneously flows through the glass tube,and light is emitted as a result of the excitation of xenon atoms ormolecules at that time. These xenon flash lamps FL have the propertiesof being capable of applying extremely intense light as compared with acontinuous lighting light source such as halogen lamps HL because theelectrostatic energy previously stored in the capacitor is convertedinto an extremely short optical pulse of 0.1 to 100 milliseconds.Accordingly, the flash lamps FL are pulse light emission lamps capableof emitting instantaneous light in an extremely short time shorter thanone second. The light emission time of the flash lamps FL iscontrollable by adjusting a coil constant of a lamp power sourcesupplying power to the flash lamps FL.

The reflector 52 is provided above the flash lamps FL to cover all ofthe flash lamps FL. A basic function of the reflector 52 is to reflectthe flash light emitted from the flash lamps FL toward the heattreatment space 65. The reflector 52 is formed of an aluminum alloyplate and has a surface (a surface that faces the flash lamps FL) thatis roughened by blasting.

The halogen heater 4 provided below the chamber 6 includes a pluralityof (in the present embodiment, 40) built-in halogen lamps HL. Thehalogen heater 4 is a light irradiation part that heats thesemiconductor wafer W with the halogen lamps HL that emit light frombelow the chamber 6 through the lower chamber window 64 to the heattreatment space 65. Light applied from the halogen heater 4 passesthrough the susceptor 74 made of quartz, and reaches the lower surfaceof the semiconductor wafer W supported on the susceptor 74.

FIG. 7 is a plan view illustrating arrangement of the plurality of thehalogen lamps HL. In the present embodiment, 20 halogen lamps HL arearranged in an upper row, and 20 halogen lamps HL are arranged in alower row. Each halogen lamp HL is a rod-shaped lamp having an elongatedcylindrical shape. The 20 halogen lamps HL in the upper row and the 20halogen lamps HL in the lower row are respectively arranged such thattheir longitudinal directions are parallel to one another along themajor surface of the semiconductor wafer W held by the holder 7 (i.e.,in the horizontal direction). Thus, both of the planes formed by thearrays of the halogen lamps HL in the upper and lower rows arehorizontal planes.

As illustrated in FIG. 7, in each of the upper and lower rows, thehalogen lamps HL are disposed at a higher density in the region thatopposes the peripheral portion of the semiconductor wafer W held by theholder 7 than in the region that opposes the central portion of thesemiconductor wafer W. That is, in both of the upper and lower rows, thepitch of arrangement of the halogen lamps HL in the peripheral portionof the array of the halogen lamps HL is shorter than that in the centralportion of the array. Accordingly, during heating with irradiation oflight from the halogen heater 4, a larger amount of light is applicableto the peripheral portion of the semiconductor wafer W where thetemperature easily drops.

Also, a lamp group of the halogen lamps HL in the upper row and a lampgroup of the halogen lamps HL in the lower row are arranged to intersecteach other in a grid-like pattern. That is, a total of 40 halogen lampsHL is disposed such that the longitudinal lengths of the halogen lampsHL in the upper row and the longitudinal lengths of the halogen lamps HLin the lower row are orthogonal to each other.

The halogen lamps HL are filament-type light sources in which current isapplied to a filament disposed in the glass tube to make the filamentincandescent and emit light. The glass tube contains a gas that isprepared by introducing a trace amount of halogen elements (e.g., iodineor bromine) into inert gas such as nitrogen or argon. The introductionof halogen elements allows the temperature of the filament to be set toa high temperature while suppressing breakage of the filament. Thehalogen lamps HL thus have the characteristics of lasting longer thantypical incandescent lamps and being able to continuously apply intenselight. That is, the halogen lamps HL are continuous lighting lamps thatcontinuously emit light for at least one or more seconds. Moreover, thehalogen lamps HL as rod-shaped lamps have a long life, and disposingtheses halogen lamps HL in the horizontal direction enhances theefficiently of radiation of the semiconductor wafer W located above thehalogen lamps.

The controller 3 controls the above-described various operatingmechanisms provided in the heat treatment apparatus 1. The hardwareconfiguration of the controller 3 is the same as that of a commonly usedcomputer. That is, the controller 3 includes a CPU that is a circuit forperforming various types of computations, a ROM that is a read-onlymemory for storing basic programs, a RAM that is a readable/writablememory for storing various types of information, and a magnetic disk forstoring software and data for control. The processing in the heattreatment apparatus 1 proceeds as a result of the CPU of the controller3 executing a predetermined processing program.

Next, the procedure of processing performed on the semiconductor wafer Wby the heat treatment apparatus 1 will be described. The semiconductorwafer W to be processed here is a semiconductor substrate doped withimpurities (ions) by ion implantation. These impurities are activatedthrough heat treatment (annealing) involving the application of flashlight by the heat treatment apparatus 1. The following procedure ofprocessing performed by the heat treatment apparatus 1 is implemented bythe controller 3 controlling each operating mechanism of the heattreatment apparatus 1.

First, the valve 84 for supplying a gas and the valves 89 and 192 forexhausting a gas are opened to start the supply and exhaust of a gasinto and from the chamber 6.

When the valve 84 is opened, treatment gas is supplied from the gassupply port 81 into the heat treatment space 65. According to thispreferred embodiment, treatment gas of nitrogen is supplied from the gassupply source 85 into the chamber 6. The flow amount of nitrogensupplied into the chamber 6 is regulated by the flow amount controlvalve 21. According to this preferred embodiment, this amount isregulated in a range from 50 L/min to 60 L/min.

The heater 22 heats nitrogen passing through the gas supply pipe 83.According to this preferred embodiment, the heater 22 heats nitrogenpassing through the gas supply pipe 83 to raise the temperature of thenitrogen to 350° C. However, this temperature of 350° C. is atemperature of nitrogen at the position where the heater 22 is provided.The temperature of the nitrogen raised to 350° C. by the heater 22 dropsto approximately 200° C. when the nitrogen reaches the inside of thechamber 6 through the gas supply port 81. This temperature drop isproduced by conduction of heat from nitrogen gas to a gas passage routesuch as the gas supply pipe 83. When the valve 89 is opened with supplyof nitrogen, the gas in the chamber 6 is exhausted from the gas exhaustport 86. By simultaneous operations of supply of nitrogen from the gassupply port 81 and discharge of gas from the gas exhaust port 86, thehigh-temperature nitrogen gas supplied from above the heat treatmentspace 65 within the chamber 6 flows downward, and flows out from belowthe heat treatment space 65. A flow of high-temperature nitrogen gas isthus formed in the heat treatment space 65 within the chamber 6.

When the valve 192 is opened, the gas in the chamber 6 is also exhaustedfrom the transport opening 66. Moreover, the atmosphere around thedriving part of the transfer mechanism 10 is also discharged by anexhaust mechanism (not shown). Supply of the high-temperature nitrogengas into the heat treatment space 65 within the chamber 6 is alreadystarted before a start of an initial treatment for a lot (a set ofsemiconductor wafers W corresponding to targets of the same treatmentcontents under the same conditions) of the semiconductor wafer W. Duringthe heat treatment of the semiconductor wafer W in the heat treatmentapparatus 1, the high-temperature nitrogen gas is continuously suppliedinto the heat treatment space 65. The amount of the supplied nitrogengas is changed as appropriate in accordance with the processing step.

Then, the gate valve 185 is opened to open the transport opening 66, andthe ion-implanted semiconductor wafer W is transported into the heattreatment space 65 of the chamber 6 through the transport opening 66 bya transport robot located outside the apparatus. The semiconductor waferW transported into the heat treatment space 65 by the transport robot ismoved to a position directly above the holder 7 and stopped. Then, thepair of transfer arms 11 of the transfer mechanism 10 moves horizontallyfrom the retracted position to the transfer operation position and movesupward, so that the lift pins 12 pass through the through holes 79 andprotrude from the upper surface of the susceptor 74 to receive thesemiconductor wafer W.

After the semiconductor wafer W is placed on the lift pins 12, thetransport robot retracts from the heat treatment space 65, and thetransport opening 66 is closed with the gate valve 185. Then, the pairof transfer arms 11 moves down, and thereby the semiconductor wafer W istransferred from the transfer mechanism 10 to the susceptor 74 of theholder 7 and held in a horizontal position from the underside. Thesemiconductor wafer W is held by the holder 7 with its impurity-dopedsurface with a pattern facing upward. The semiconductor wafer W is alsoheld inward of the five guide pins 76 on the upper surface of thesusceptor 74. The pair of transfer arms 11 that has moved down to belowthe susceptor 74 is retracted to the retracted positions, i.e., to theinside of the recessed portion 62, by the horizontal movement mechanism13.

After the semiconductor wafer W is held in a horizontal position fromthe underside by the holder 7 made of quartz, all of the 40 halogenlamps HL of the halogen heater 4 are turned on in unison to startpreheating (assist-heating). The halogen light emitted from the halogenlamps HL passes through the lower chamber window 64 and the susceptor74, which are made of quartz, and is applied to the rear surface (mainsurface on the side opposite to the front surface) of the semiconductorwafer W. The semiconductor wafer W that has received the light emittedfrom the halogen lamps HL is preheated, and thereby the temperature ofthe semiconductor wafer W increases. Note that the transfer arms 11 ofthe transfer mechanism 10, which have already retracted into therecessed portion 62, will not impede the heating using the halogen lampsHL.

During preheating with the halogen lamps HL, the temperature of thesemiconductor wafer W is measured with the contact-type thermometer 130.Specifically, the contact-type thermometer 130 with a built-inthermocouple is brought into contact with the lower surface of thesemiconductor wafer W held by the holder 7 through the cut-out portion77 of the susceptor 74 and measures the increasing wafer temperature.The measured temperature of the semiconductor wafer W is transmitted tothe controller 3. The controller 3 controls the output of the halogenlamps HL while monitoring whether the temperature of the semiconductorwafer W raised by the application of light from the halogen lamps HL hasreached a predetermined preheating temperature T1. More specifically,the controller 3 performs feedback control of output from the halogenlamps HL on the basis of measurements received from the contact-typethermometer 130 so that the temperature of the semiconductor wafer Wbecomes the preheating temperature T1. The preheating temperature T1 isset to about 200° C. to 800° C. at which the impurities doped in thesemiconductor wafer W are not caused to be diffused by heat, andpreferably, may be set to about 350° C. to 600° C. (in the presentembodiment, 600° C.). Note that when the temperature of thesemiconductor wafer W is increased by the application of light from thehalogen lamps HL, the radiation thermometer 120 does not measure thetemperature. This is because precise temperature measurement is notpossible with the halogen light from the halogen lamps HL entering theradiation thermometer 120 as disturbance light.

After the temperature of the semiconductor wafer W reaches thepreheating temperature T1, the controller 3 temporarily maintains thesemiconductor wafer W at the preheating temperature T1. Morespecifically, when the temperature of the semiconductor wafer W measuredwith the contact-type thermometer 130 reaches the preheating temperatureT1, the controller 3 controls output from the halogen lamps HL tomaintain the temperature of the semiconductor wafer W approximately atthe preheating temperature T1.

This preheating with the halogen lamps HL allows the temperature of theentire semiconductor wafer W to uniformly increase to the preheatingtemperature T1. In the preheating stage using the halogen lamps HL, thetemperature of the peripheral portion of the semiconductor wafer W,where heat more easily dissipates, tends to drop lower than thetemperature of the central portion. On the other hand, the halogen lampsHL in the halogen heater 4 are arranged with higher density in theregion facing the peripheral portion of the semiconductor wafer W thanin the region facing the central portion of the semiconductor wafer W(see FIG. 7). Accordingly, a larger amount of light is applied to theperipheral portion of the semiconductor wafer W where heat easilydissipates. In this condition, the in-plane temperature distribution ofthe semiconductor wafer W becomes uniform in the preheating stage.Moreover, the mirror-finished inner circumferential surface of thereflection ring 69 attached to the chamber side portion 61 increases theamount of light reflected by the inner circumferential surface of thereflection ring 69 toward the peripheral portion of the semiconductorwafer W. Accordingly, the in-plane temperature distribution of thesemiconductor wafer W becomes more uniform in the preheating stage.

After an elapse of a predetermined period from the time when thetemperature of the semiconductor wafer W reaches the preheatingtemperature T1 by application of light from the halogen lamps HL, theflash lamps FL of the flash heater 5 apply flash light to the frontsurface of the semiconductor wafer W. At this time, part of the flashlight emitted from the flash lamps FL travels directly into the chamber6, and part of the flash light is reflected by the reflector 52 and thentravels into the chamber 6. The application of such flash light enablesflash heating of the semiconductor wafer W.

The flash heating implemented by the application of flash light from theflash lamps FL allows the surface temperature of the semiconductor waferW to be increased in a short time. That is, the flash light emitted fromthe flash lamps FL is extremely short intense flash light that isobtained by converting the electrostatic energy previously stored in thecapacitor into an extremely short optical pulse and that has anirradiation time of about 0.1 to 100 milliseconds. The surfacetemperature of the semiconductor wafer W heated with the flash lightemitted from the flash lamps FL instantaneously rises to a treatmenttemperature T2 of 1000° C. or higher, and then drops rapidly after theactivation of impurities doped in the semiconductor wafer W. In thisway, the heat treatment apparatus 1 allows the surface temperature ofthe semiconductor wafer W to rise and drop in an extremely short time,and thereby enables the activation of impurities doped in thesemiconductor wafer W while suppressing the diffusion of impurities dueto heat. Since the time required for the activation of impurities isextremely shorter than the time required for heat diffusion ofimpurities, the activation is completed even in such a short time ofabout 0.1 to 100 milliseconds that causes no diffusion.

After completion of the flash heat treatment and an elapse of apredetermined period of time, the halogen lamps HL are also turned off.The temperature of the semiconductor wafer W thus rapidly drops from thepreheating temperature T1. The decreasing temperature of thesemiconductor wafer W is measured with the contact-type thermometer 130or the radiation thermometer 120, and the measurement result istransmitted to the controller 3. On the basis of the measurement result,the controller 3 monitors whether the temperature of the semiconductorwafer W has dropped to a predetermined temperature. After thetemperature of the semiconductor wafer W has dropped to thepredetermined temperature or less, a pair of the transfer arms 11 of thetransfer mechanism 10 are moved horizontally again from the retractedpositions to the transfer operation position and moved upward, so thatthe lift pins 12 protrude from the upper surface of the susceptor 74 andreceive the heat-treated semiconductor wafer W from the susceptor 74.Then, the transport opening 66 closed by the gate valve 185 is openedand the semiconductor wafer W placed on the lift pins 12 is transportedby the transport robot located outside the apparatus. This completes theheat treatment of the semiconductor wafer W in the heat treatmentapparatus 1.

The semiconductor wafer W to be treated contains various types of filmssuch as a resist film and an insulation film in a certain case. Whenflash light is applied to the semiconductor wafer W containing thesefilms for heat treatment, carbon contaminants may be discharged into theheat treatment space 65 within the chamber 6 as a result of combustionof the films and volatilization of residual solvent components, forexample. When the contaminants diffused into the heat treatment space 65adhere to the inner wall surface of the chamber 6 or the structureinside the chamber such as the susceptor 74, the contaminant adhesionportion is contaminated. This contamination becomes not only acontamination source for a subsequent semiconductor wafer W, but also afactor causing disorder of illuminance distribution of the semiconductorwafer W during light irradiation and heating.

According to this embodiment, therefore, high-temperature treatment gasheated by the heater 22 is supplied into the heat treatment space 65within the chamber 6 to form a gas flow. With the flow of thehigh-temperature treatment gas through the chamber 6, contaminantsdischarged from the films of the semiconductor wafer W during heattreatment are discharged to the outside of the chamber 6 for reductionof contamination inside the chamber 6. As a result, contamination of theinner wall surface of the chamber 6, and of the structure inside thechamber such as the susceptor 74 decreases.

For producing an effect of reducing adhesion of contaminants to thestructure inside the chamber by utilizing supply of the high-temperaturetreatment gas, the temperature of the treatment gas passing through thegas supply pipe 83 needs to be raised to 100° C. or higher by the heater22 at the time of supply of the gas into the chamber 6. Thecontamination reduction effect increases as the temperature of thetreatment gas rises.

However, supply of treatment gas having an excessively high temperatureinfluences the heat treatment for the semiconductor wafer W.Accordingly, the treatment gas passing through the gas supply pipe 83needs to be heated by the heater 22 such that the temperature of thetreatment gas is maintained lower than a set treatment temperature ofthe semiconductor wafer W at the time of supply of the gas into thechamber 6. When multiple levels are set for the treatment temperature ofthe semiconductor wafer W, the heater 22 heats the treatment gas suchthat the temperature of the treatment gas supplied into the chamber 6 ismaintained lower than the lowest set treatment temperature in themultiple levels. According to this preferred embodiment, the heater 22heats nitrogen gas passing through the gas supply pipe 83 such that thetemperature of the nitrogen gas is maintained lower than the preheatingtemperature T1 at the time of supply of the gas into the chamber 6.

Moreover, supply of high-temperature treatment gas into the chamber 6produces a cleaning effect for removing contaminants already adhering tothe inner wall surface of the chamber 6 and the structure inside thechamber such as the susceptor 74.

The effect of discharging contaminants to the outside of the chamber 6increases as the flow amount of treatment gas supplied into the chamber6 increases. Accordingly, adhesion of contaminants to the structureinside the chamber further decreases with a larger flow amount of thetreatment gas. According to this preferred embodiment, the flow amountcontrol valve 21 supplies a larger flow amount of nitrogen gas, i.e., ina range from 50 L/min to 60 L/min, into the chamber 6 instead of anormal flow amount ranging from 20 L/min to 30 L/min. In this case,contaminants are discharged to the outside of the chamber 6 beforeadhering to the structure inside the chamber. Accordingly, contaminationwithin the chamber 6 more effectively decreases.

Assuming that an inside volume of the chamber 6 is D, the flow amount oftreatment gas to be supplied into the chamber 6 may be set in a rangefrom 0.5 D/min to 5 D/min. This large amount of supply of treatment gasinto the chamber 6 increases the effect of discharging contaminants tothe outside of the chamber 6, thereby effectively reducing contaminationwithin the chamber 6.

While the above has been a description of a preferred embodiment of thepresent invention, various modifications in addition to those describedabove may be made to the present invention without departing from thescope and spirit of the invention. According to the preferred embodimentdescribed herein, high-temperature nitrogen gas is supplied into thechamber 6. However, the type of treatment gas is not limited to nitrogengas, but may be other types such as oxygen and argon. Particularly,supply of highly reactive heated treatment gas such as oxygen into thechamber 6 increases the cleaning effect for removing contaminantsalready adhering to the structure inside the chamber.

While the flash heater 5 includes 30 flash lamps FL in theabove-described preferred embodiment, the present invention is notlimited to this example. The flash heater 5 may include an arbitrarynumber of flash lamps FL. The flash lamps FL are not limited to xenonflash lamps, and may be krypton flash lamps. The number of halogen lampsHL included in the halogen heater 4 is also not limited to 40, and thehalogen heater 4 may include an arbitrary number of halogen lamps HL aslong as each of the upper and lower rows includes the array of aplurality of halogen lamps.

The light irradiation part which applies light to the semiconductorwafer W for heating is not limited to the flash lamps FL and the halogenlamps HL, but may be a laser beam source.

Also, substrates to be processed by the heat treatment apparatus of thepresent invention are not limited to semiconductor wafers, and may beglass substrates for use in a flat panel display such as a liquidcrystal display device, or substrates for solar cells. The technique ofthe present invention is also applicable to other applications such asheat treatment of a high dielectric gate insulating film (high-k film),bonding of metal and silicon, and crystallization of polysilicon.

While the invention has been shown and described in detail, theforegoing description is in all aspects illustrative and notrestrictive. It is therefore understood that numerous modifications andvariations can be devised without departing from the scope of theinvention.

What is claimed is:
 1. A heat treatment apparatus that heats a substrateby irradiating the substrate with light, comprising: a chamber thataccommodates the substrate; a susceptor provided in said chamber andsupporting the substrate; a light irradiation part that applies light tothe substrate supported on said susceptor; a gas supply part thatsupplies treatment gas into said chamber; and a gas heater that heatssaid treatment gas supplied from said gas supply part to said chamber.2. The heat treatment apparatus according to claim 1, wherein said gasheater heats said treatment gas supplied into said chamber to raise atemperature of said treatment gas to 100° C. or higher.
 3. The heattreatment apparatus according to claim 1, wherein said treatment gas isnitrogen, oxygen, or argon.
 4. The heat treatment apparatus according toclaim 1, further comprising a flow amount increasing part that increasesa flow amount of said treatment gas supplied from said gas supply partto said chamber.
 5. The heat treatment apparatus according to claim 1,wherein said light irradiation part includes a flash lamp that appliesflash light to the substrate from one side of said chamber.
 6. The heattreatment apparatus according to claim 5, wherein said light irradiationpart further includes a halogen lamp that applies light to the substratefrom the other side of said chamber.
 7. A heat treatment method thatheats a substrate by irradiating the substrate with light, comprisingsteps of: (a) supporting the substrate on a susceptor within a chamber;(b) supplying treatment gas into said chamber; and (c) applying light tothe substrate supported on said susceptor, wherein said step (b)includes a step of (b-1) heating said treatment gas supplied to saidchamber.
 8. The heat treatment method according to claim 7, wherein saidstep (b-1) heats said treatment gas supplied into said chamber to raisea temperature of said treatment gas to 100° C. or higher.
 9. The heattreatment method according to claim 7, wherein said treatment gas isnitrogen, oxygen, or argon.
 10. The heat treatment method according toclaim 7, wherein said step (b) further includes a step of (b-2)increasing a flow amount of said treatment gas supplied to said chamber.11. The heat treatment method according to claim 7, wherein said step(c) applies flash light to the substrate from one side of said chamberby using a flash lamp.
 12. The heat treatment method according to claim11, wherein said step (c) further applies light to the substrate fromthe other side of said chamber by using a halogen lamp.